/Engine/Source/Runtime/Core/Public/Containers/Map.h
No need to rehash after calling. The hash table must be properly hashed before calling.
The address to the value, not the pair
void * FindOrAdd ( const void * Key, const [FScriptMapLayout](API\Runtime\Core\Containers\FScriptMapLayout) & Layout, [TFunctionRef](API\Runtime\Core\GenericPlatform\TFunctionRef)< uint32(const void *)> GetKeyHash, [TFunctionRef](API\Runtime\Core\GenericPlatform\TFunctionRef)< bool(const void *, const void *)> KeyEqualityFn, [TFunctionRef](API\Runtime\Core\GenericPlatform\TFunctionRef)< void(void *, void *)> ConstructPairFn )